1. Technical Field
The present disclosure relates to apparatus and methods for constructing composite members.
2. Description of Related Art
Composite items are typically constructed from layers of material that are laminated together. Some categories of materials used to fabricate composite items include fiber, fabric, tape, film and foil, and each of these categories includes a multitude of diverse materials. For example, typical fibers include glass, carbon, aramid, and quartz. When these fibers are arranged as woven sheets and unidirectional ribbons, they are referred to as fabric and tape, respectively.
Material placement is a process used to construct or fabricate composite items. These composite items include relatively simple planar sheets or panels to relatively large complex structures. Many composite items are built up from multiple layers or plies of composite materials. Some composite materials may be pre-impregnated with uncured resin (“prepreg”) or another binding agent.
In some applications an end effector of a machine for fabricating composite members arrays a group of prepreg tows into a continuous band and then presses them against the surface of a workpiece. Generally a compaction roller performs the task of pressing the tows against the workpiece. To accommodate misalignments between the end effector and the workpiece and elevation variations on the surface of the workpiece, the compaction roller is generally movable toward and away from the end effector. Unfortunately, movement of the compaction roller tends to reduce tension in the tows, which can cause rewinding of the spools that supply the tow, can degrade the quality of the lay-up and can contribute to despooling problems.